[thawt]

The problem with OPTIONS is it doesn't describe anything about the data the resource returns.

I really wish there was a DESCRIBE verb that would return a structure of what is expected to be received/sent.

Then microformats could spring up around datatypes returned by DESCRIBE. This is of course very XML.

Edit: This would also allow for automatic discovery of new APIs.

[steveklabnik]

That's what resources that have form-style affordances offer. See, for example, Collection+JSON.